Return of the Elf: Making a 1976 microcomputer more user friendly

A home-brew programmer for the low-power Membership Card microcomputer

4 min read
Return of the Elf: Making a 1976 microcomputer more user friendly
Photo: Randi Klett

A couple of months ago, I built the Membership Card, a remake of the 1976 Cosmac Elf microcomputer. Despite the vintage of its RCA CDP1802 processor, the Membership Card still has value as a low-power microcontroller, with an elegant instruction set that leverages a clever hardware design. However, only a masochist would attempt to do any serious programming with the Membership Kit alone: Entering a program via the Membership Card’s front panel requires using toggle switches to enter bytes into memory, one bit at a time.

What’s needed is a way to upload programs written with the aid of those sops to human frailty, keyboards and screens. There are actually a number of ways to get such programs into the Membership Card, which is composed of one circuit board that is a complete microcomputer, with processor and memory, and another board stacked above it, which is the front panel that provides general input/output facilities. One way is to burn a program directly into an EEPROM chip and mount it on the microcomputer board. A more flexible option is to burn a small loader program onto an EEPROM and then upload programs as desired via a serial connection.

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Why Functional Programming Should Be the Future of Software Development

It’s hard to learn, but your code will produce fewer nasty surprises

11 min read
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A plate of spaghetti made from code
Shira Inbar
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You’d expectthe longest and most costly phase in the lifecycle of a software product to be the initial development of the system, when all those great features are first imagined and then created. In fact, the hardest part comes later, during the maintenance phase. That’s when programmers pay the price for the shortcuts they took during development.

So why did they take shortcuts? Maybe they didn’t realize that they were cutting any corners. Only when their code was deployed and exercised by a lot of users did its hidden flaws come to light. And maybe the developers were rushed. Time-to-market pressures would almost guarantee that their software will contain more bugs than it would otherwise.

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